Redevelopment of Alter Mainzer Tunnel
The route between Mainz Central Station and the Mainz South Station was built between 1881 and 84 as a twin-track tunnel. On account of pronounced damage, during the 1930s, a 300 m long section of the tunnel was relocated in a deep cutting so that the former 1,200 m long tunnel was divided up into the Central Station and Mainz South tunnels. The route is now to be expanded to take 4 tracks in conjunction with the development of the Mainz-Mannheim main line. Towards this end, the twin-track, 1,296 m long Neue Mainzer Tunnel was opened in 2003 to the south of the 2 existing Mainz tunnels. From 2006 to 2009, the existing tunnels are to be upgraded through an enlargement in keeping with the DB AG's current code of practice. Inner-urban tunnelling with shallow overburdens calls for extremely careful planning and construction. Numerous streets and buildings are located in the tunnel's sphere of influence and generally the overlying ground is no more than 10 to 20 m deep. The cross-section is mainly located in tertiary silts and clays, which are interspersed and underlaid by sands and occasional sandstone banks. The enlargement to attain the new 75 m² useful cross-section requires 24 m³ of masonry to be removed and 53 m³ of rock to be excavated per tunnel metre. The cross-section is to be secured in short lengths of advance with shotcrete and will be provided with a reinforced concrete lining. Excavation classes 5 and 7 are expected to be applied with injection lances, forepoling plates and pipe umbrellas used for advance supporting. As the supporting measures provided by the drive will not be sufficient to ensure the stability of certain buildings, fan-shaped jetting injections can be undertaken from shafts prior to the driving operations in order to avoid damage so that the foundations of the buildings are substantially improved. Subsequent injections can then be executed from these shafts via the fan-shaped boreholes, in order to be able to compensate for settlement between the individual excavation states caused by tunnelling.
- Country: Germany
- Region: Rhineland Palatinate
- Tunnel utilization: Traffic
- Type of utilization: Main-line rail
- Client: DB Netz AG
- Consulting Engineer: DB Projektbau GmbH, ILF, ELE Erdbaulaboratorium Essen
- Main construction method: Redevelopment
- Lining: Concrete formwork?
- No. of tubes: 1
- Tunnel total length: 663 m long Central Station Tunnel, 246 m long Mainz Süd Tunnel
- Cross-section: enlargement from 45 to 75 m² above upper edge of rail
- Contract Volume: € 52 million
- Construction start/end: 2006 to 2009